Urinalysis involves chemical testing of the urine for clinically important chemically detectable constituents and parameters, and examining centrifuged sediment from the urine sample under magnification so as to identify and semi-quantitate the presence of formed bodies in the urine. A general discussion of the present state of the art relating to urinalysis is presented in an article authored by Jonathan Ben-Ezra et al, in Clinical Chemistry, Vol 44:1, pages 92-95 (1998).
Chemical testing of a urine sample generally involves analyzing the urine for one or more of the following constituents: glucose; bilirubin; ketones; blood; albumen; nitrites; red blood cells and free hemoglobin; leukocyte esterase; pH; urobilinogin; ascorbic acid; and specific gravity. These various determinations are made through the use of a dipstick having various chemical reagent bands printed thereon. Such dipsticks are commercially available from Bayer Corporation of Elkhart, Ind., as well as other commercial sources. The dipstick is dipped into a well mixed urine sample, and after a time period of thirty seconds to two minutes, the various reagent bands are visually or optically examined for color changes. The bands can be visually compared to a preprinted color chart in order to determine the amount of each of the constituents or parameters being measured. It is also possible to optically scan the dipstick and thereby obtain instrument readings of color intensity or wave length through the use of an instrument manufactured by Ames. Currently available instruments for optically scanning the dipstick bands do not distinguish lysed red blood cells from intact red blood cells, since lysed red blood cells create a different, color distribution on the blood band than do intact red blood cells. With lysed cells, the reaction color is relatively evenly distributed over the blood band, while with whole cells, the reaction color tends to be spotted on the blood band. Presently available instruments do not quantify the number of spots formed on the blood band from whole cells, but can merely quantify the overall color intensity sensed on the band.
In present day technology for quantitatively analyzing a urine sample for the presence of formed bodies such as both red and white blood cells; bacteria; crystals; fecal matter; parasites; spermatozoa; ova from parasites; as well as other formed bodies such as casts, the urine sample is centrifuged so as to separate the liquid phase from the formed body sediment in the urine, thereby concentrating the sediment. Ninety to ninety five percent of the liquid phase is then drawn off from the sediment and discarded, the sediment is re-suspended in the remaining liquid, and a drop of the resuspended sediment is examined under magnification on a microscope slide at low power, i.e., about 100.times., for the presence or absence of one or more of the aforesaid formed bodies which are morphologically distinguishable, one from another. This type of analysis provides a crude quantification of target formed bodies which are present in urine.
In present day technology for detecting rare events such as casts in the urine sample, the urine sample sediment is examined as above on a microscope slide. Proteinacious casts which are casts of the renal tubules, may be found in small quantities in normal urine. They may be described by the type of cells they contain such as those having included red cells, which are called red cell casts. The red cell casts are formed in the kidney and are indicative of bleeding in the kidneys prior to the renal collecting ducts and therefore can provide useful information to the clinician. White blood cell casts are indicative of infection of the kidney itself, as opposed to infection in just the urinary bladder. Types of casts include red cell casts, white cell casts, tubular epithelial cell casts, granular or waxy casts containing degenerated cellular components, and clear or hyaline casts. Other than hyaline casts, casts are rarely seen in normal healthy patients, and the range of quantity is described in the literature.
Instruments have been developed which both determine the chemical constituents of the urine and also assist in the microscopic analysis. Such an instrument is the Yellow IRIS, which automatically places the sample on the urine dipstick and then reads the chemical results. For analyzing the particulate components, urine is passed through a flow cell, where a high speed camera captures the images of the particles as they pass through the flow cell and then displays the images so that the technician can classify them. This approach requires less technological time than a purely manual approach, but the instrument is very expensive, prone to malfunctions, and requires a technologist to interpret the particulates which are photographed.
It would be highly desirable to have a single system which could be used to perform a complete urine sample analysis, i.e., urine chemistry, urine blood cell counts, urine bacteria counts, rare event detection, all without significant human intervention, and in an uncomplicated and reliable instrument.